1. Field of the Invention
The present invention relates to a two-dimensional optical deflector.
2. Description of the Related Art
U.S. Pat. No. 6,108,118 discloses an electromagnetic-driven two-dimensional optical deflector. As shown in FIG. 15, in this optical deflector, a support 403 is connected to an outer movable plate 401a through an outer torsion bar 402a, and the outer movable plate 401a is connected to an inner movable plate 401b through an inner torsion bar 402b. The outer torsion bar 402a and inner torsion bar 402b extend perpendicular to each other. The outer movable plate 401a is provided with an outer driving coil 404a. Part of an outer driving coil wiring extending from the outer driving coil 404a extends to an electrode on the support 403. The inner movable plate 401b is provided an inner driving coil 404b. Part of an inner driving coil wiring extending from the inner driving coil 404b extends to an external electrode (an electrode on the outer torsion bar 402a in FIG. 15) via on the outer movable plate 401a. 
In order to make magnetic fields act on the outer driving coil 404a and inner driving coil 404b, two permanent magnets 407a for driving the outer movable plate are arranged on two sides of the outer movable plate 401a, and two permanent magnets 407b for driving the inner movable plate are arranged on two sides of the inner movable plate 401b. The two permanent magnets 407b are fixed to yokes 418. By supplying proper AC currents to the outer driving coil 404a and inner driving coil 404b, the inner movable plate 401b is oscillated on the outer torsion bar 402a and inner torsion bar 402b serving as rotation axes. This makes it possible to two-dimensionally deflect a light beam reflected by the inner movable plate 401b. 
The outer movable plate 401a is provided with a Hall element 411a for the detection of a deflection angle. A Hall element wiring 409a extending from the Hall element 411a extends to an electrode on the support 403. The inner movable plate 401b is provided with a Hall element 411b for the detection of a deflection angle. A Hall element wiring 409b extending from the Hall element 411b extends to an external electrode (an electrode on the outer torsion bar 402a in FIG. 15) via on the outer movable plate 401a. 